The prior art is replete with many categories of exercise machines designed to exercise all major muscle groups of the human body. The most popular machines provide motion similar to activities such as bicycling, skiing, walking or stepping. The popularity of these machines is due to the effective low impact form of exercise enabled, as well convenience and time saving advantages.
In reference to machines such as stationary bicycles and steppers which involve the lower body, and cause the operators feet to move under resistance along constrained arcuate paths, evolving bicycle and stepper machine designs continue to incorporate foot motion paths of arcuate forms which are circular by definition. With bicycle machines, the circular path is caused by the simple relationship of the distance between the foot pedal and the pedal crank shaft. This constancy of motion is artificial to the human body, and is not considered by the inventor to be optimum during exclusive use for long term muscular development and conditioning. Bicycle machines do however offer a continuous motion which is preferable in order to ensure machine usage.
In reference to stepper machines, the arcuate path that the foot platforms travel about is a simple function of the distance between the foot platform and the pivot point of the platform support member. The stop and go motion of conventional steppers, in conjunction with the somewhat linear foot path, is considered by the inventor to be less ergonomic than the four bar stepper design of the present invention.
If one studies the motion paths of human feet during an activity such as walling or running, it will readily be observed that they travel along paths more accurately described as teardrop shaped. Whereas in the case of hill or stair climbing, the motion of ones feet closely resembles an ellipse or oval. The present invention provides a means to satisfactorily produce either motion, teardrop or elliptical, and does so in an efficient and economical way.
The present invention provides a means to generate a number of characteristically distinct closed curves by using an arrangement of linkages. In all of the embodiments of this invention, the motion output of the linkages occurs at the foot pedals or foot platforms. Output of the linkages is also illustrated in several figures to additionally interface with a persons arms or hands in order to exercise upper body muscles.
Generally, the dynamic linkage portion of the mechanism may be described as containing three pin connected links, and in most of the illustrated embodiments, these link assemblies are interconnected by a common crank shaft In this text the general terms for these three dynamic links are crank, connector, and rocker. The frame of the machine serves as a fourth stationary link. The length of each of these four links, in combination with the arrangement in which they are pinned together, establishes the desired output exercise curve.
The first link is the shortest of the four links and is referred to as a crank link. The crank link is not to be considered figuratively as a drive link because this link receives force and is caused to rotate due to actions of the machine operator. It is possible however to drive this crank link independently by a motor or such if the design of a powered exercise machine is desired.
In the embodiments which provide a common crank shaft between a right and a left foot or hand receiving member, the attached cranks are diametrically opposed as to operate out of phase with respect to each other by 180 degrees. This phase difference of 180 degrees is not directly equatable to the relative positions of the foot platforms due to differences of instantaneous velocity or accelerations of the foot platforms at different path points. For the linkage system shown in the first figure, the platforms are positionally maintained out of phase by approximately 180 degrees, and the operator would not sense an imbalance of platform velocity or acceleration.
On those linkage mechanisms which generate pedal path curves where significant imbalance is present, it is not to be considered a disadvantage. When one considers the motion one""s feet experience on your average walk or hike on rough ground, the feet experience quite random, unequal, and unsynchronous paths and velocities. The inventor, having traversed uncounted miles of rough forested terrain can speak with authority as to the physical benefits derived from such variable and random action.
Although the most popular application of this invention would subject both feet along separate elliptical paths on two foot platforms out of phase with respect to each other by 180 degrees, another embodiment, intended primarily for a recumbent style exercise machine provides only one, relatively wide foot platform. In this embodiment the user reclines on a sloped bench and pumps the foot platform throughout an elliptical path with both feet side by side in a continuous, momentum gaining manner. This form of exercise is intended to be similar to squatting and standing exercises while eliminating strain and potential injury to back muscles.
Continuing now, the second link, referred to as a connector link, is rotatably attached to both the crank and the rocker. The foot platforms and/or hand receiving members are also rotatably attached to this connector link such that a total of at least three pin joints are always present and utilized at the connector link. The connector link cyclically translates while rotating a limited amount during machine operation.
The third link, referred as a rocker, is attached to the frame or stationary link at one end, and to the connector link at its opposite end. This rocker link will never completely revolve, but rather swing back and forth a limited amount.
The stationary link or fourth link rotatably secures the crank and the rocker to the machine frame.
In the preferred embodiment, the connector link is rotatably mounted at one distal end to the crank, and at an opposite distal end to a foot platform. Offset and between these opposite distal ends the crank is rotatably secured.
In order to ensure smoothest operation while cycling the foot platforms, particularly while they are at their minimum and maximum defection point, a flywheel may be coupled to the crankshaft.